2003 ford expedition i just got it a week ago and the front heat works great but the back vents only blow cold air. How do i fix this?

SOURCE: 2004 Ford Expedition rear floor cool/heat

Item Part Number Description 1 — Air inlet door 2 — Temperature blend door 3 — Headliner airflow 4 — Auxiliary mode door 5 — Floor airflow 6 18476 Heater core 7 19860 Evaporator core 8 19805 Blower motor
The auxiliary A/C and heating system has the following features:

• The auxiliary A/C and heating system is functional whenever the instrument panel mounted A/C control is in any position except OFF.
• The auxiliary blower motor recirculates the air inside the vehicle. Outside air is not available to the auxiliary system.
• Air is cooled and dehumidified by the auxiliary A/C evaporator core only if the instrument panel mounted A/C control is adjusted to a position that requires A/C compressor operation.
• The temperature blend door and the auxiliary mode door are controlled by electric actuator motors.
• Movement of the auxiliary temperature control between COOL and WARM causes a corresponding movement of the temperature blend door to mix air flowing through and around the auxiliary heater core.
• Movement of the auxiliary mode control between PANEL and FLOOR causes a corresponding movement of the auxiliary mode door to direct air flow between the panel (headliner) registers and the floor duct.

1. Remove the RH quarter trim panel cup holder and access panel.

1. Remove the screws.

1. Disconnect the blend door actuator electrical connector.

1. To install, reverse the removal procedure.

SOURCE: Vent control

You have a vacuum leak.Defrost is the default postion(no vacuum).
See if you can locate the small black vacuum line that goes inside the vehicle on the passenger side near the heater core. The trace it back,should see it going to a canister then to the intake manifold.Make sure it is not disconnected or broken somewhere.

SOURCE: heater is blowing but its cold air not hot air 2000 expedition

Make sure the heater core is in the open position by using the shut off valve and turning it to open. next, you may have a malfunction in the direction door the directs the air flow in the dash. a lever may have become lose or separated. may be a bad servo motor not directing the door to move to the heater position. i would start by checking that shut off valve first on the heater core.

SOURCE: 2000 Ford Expedition front air not blowing

TRY JUMPING THE BLOWER MOTOR APPLY 12 VOLTS TO THE MOTOR IF IT STARTS THEN THE PROBLEM WOULD BE THE SWITCH IF IT DOES NOT START THEN THE MOTOR IS THE PROBLEM GOOD LUCK HOPE THIS HELPS

SOURCE: my ac blows hot air from the front vents

Expansion valve or orfice tube clog.to front unit.